Page 111 - Buried Pipe Design

Design of Gravity Flow Pipes 87

TABLE 3.3 Values of Bedding Constant K
Bedding angle, degree K
0 0.110
30 0.108
45 0.105
60 0.102
90 0.096
120 0.090
180 0.083

Table 3.3 contains a list of bedding factors K dependent upon the bed-
ding angle. These were determined theoretically by Spangler and
published in 1941. As a general rule, a value of K 0.1 is assumed.
In 1958, Reynold K. Watkins, a graduate student of Spangler, was
investigating the modulus of passive resistance through model studies
and examined the Iowa formula dimensionally. 56 The analysis deter-
mined that e could not possibly be a true property of the soil in that its
dimensions are not those of a true modulus. As a result of Watkins’
effort, another soil parameter was defined. This was the modulus of soil
reaction E er. Consequently, a new formula called the modified Iowa
formula was proposed. This equation is also often referred to as

R. K. Watkins, Circa 2001.